A medical worker injects a man with a dose of the COVID-19 vaccine at a hospital in Accra, capital of Ghana, May 19, 2021.Seth | Xinhua News Agency | Getty ImagesTop health officials in Europe and Africa said Wednesday they are worried about the potential emergence of new Covid variants that could render current vaccines useless.Dr. John Nkengasong, director of Africa’s Centres for Disease Control and Prevention, said he is “very concerned” about the emergence of a vaccine-resistant variant as the Delta variant first detected in India continues to spread around the world. Studies have shown that current vaccines work against the new variant, although not as well as they do against the original wild type virus. “It is increasingly concerning that this pandemic will be driven by the cycle of occurrence and reoccurrence of different variants,” Nkengasong said at The Wall Street Journal’s Health Tech conference. “The speed at which these viruses overtake the existing viruses is amazing.”The Delta variant was first identified by scientists in October has since spread to more than 62 countries, dominating the U.K. and now responsible for more new infections in the country than the Alpha variant — which was first detected in the U.K.Dr. Sharon Peacock, executive chair of Covid-19 Genomics U.K. Consortium, said the Delta variant is about 40% to 50% more transmissible than the Alpha variant, formerly called B.1.1.7, a strain that emerged from the U.K. last fall and was more contagious than the original virus.”So, given that level of transmissibility, I would anticipate that (the Delta variant) would’ve actually spread around the world,” she said at the conference. Peacock added the Delta variant is already present in most U.S. states, but the spread is at an early stage.White House senior medical advisor, Dr. Anthony Fauci told reporters yesterday that the U.S. needs to vaccinate more people before the Delta variant takes hold in the country.The Alpha variant is currently the dominant variant in the U.S., but the Delta variant could soon take over like it did in the U.K. “We cannot let that happen in the United States,” Fauci said yesterday.”I would be concerned … that this will be something that will be able to out-compete other circulating variants in the way that we’ve observed in the United Kingdom,” Peacock said. She also said that variants are more likely to emerge in partially vaccinated areas. Some states in the U.S. have vaccination rates higher than 70%, while others lag behind at 40%.Scientists in the U.S. are currently sequencing just 1.6% of new infections, Peacocks said. She and Nkengasong agreed that increased genomic surveillance is an important way to track the spread of new variants before they take hold.